Conventionally, an automatic pool cleaner (“APC”) may be considered either “hydraulic” or “electric” depending on the source of energy employed to effect its movement within a pool, spa, or other water-containing vessel. “Electric” cleaners, sometimes also called “robots,” typically use electricity to power motors used to drive wheels or treads to allow the cleaners to move throughout the vessel. Although on-board batteries are sometimes considered to supply electricity to the robots, more likely electricity from mains outside the vessels is conveyed via electrical cords to the robots within the vessels.
“Hydraulic” cleaners, by contrast, connect to external pumps and utilize water flow caused by operation of the pumps to effect their movement within a pool or spa. Some hydraulic cleaners connect to pump outlets; these devices are called “pressure-side” APCs, as pressurized water from pump outlets typically drives the cleaners. Alternatively, hydraulic cleaners may connect to inlets of pumps. These “suction-side” cleaners often include valves and supporting structure designed periodically to interrupt water flow through their bodies to the pumps. Periodic flow interruption creates a “water-hammer” effect, with the resulting energy used to move the APCs within pools.
U.S. Pat. No. 4,742,593 to Kallenbach discloses exemplary valves useful in water-interruption, suction-side hydraulic APCs. A flexible-walled, “diaphragm” valve of the Kallenbach patent may be placed within a chamber of a body of an APC, with the chamber filling with water upon immersion of the APC within a pool. As noted therein:                Expansion of the valve and release for it to reassume its relaxed condition is by the creation of a pressure differential across the valve member walls, i.e., a pressure difference between the chamber and the interior of the valve member. This is created by the suction [of the external pump]. The valve is autonomously opened and closed. Applied suction initially causes the valve to open; but with water flow established, the pressure within [the] valve drops below that of [the] chamber. The valve thus closes. The cycle autonomously repeats.See Kallenbach at col. 2, 1. 64 to col. 3, 1. 6 (numerals omitted).        
Similar water-interruption valves and associated structures are illustrated in U.S. Pat. No. 4,642,833 to Stoltz, et al. Like the valves of the Kallenbach patent, those of the Stoltz patent are positioned within chambers. In at least some embodiments of the Stoltz patent, water may flow into and out of the chambers via ports communicating with flow passages though the valves. See, e.g., Stoltz at col. 3, 11.8-21.
Historically, hydraulic cleaners—and especially suction-side, water-interruption APCs—have been entirely mechanical devices, operating without any need for electricity. As electronic processors (and other electric devices) decrease in cost, weight, and size, however, hydraulic cleaners could benefit from on-board inclusion of these processors and devices. Inclusion requires a supply of electricity, however, just as is required currently for electric cleaners. Such supply could, of course, likewise be provided by electric mains via a cord or perhaps by an on-board battery or turbine. Each of these approaches is disadvantageous in at least some respects, however.